The present invention pertains to guidance methods, in which missiles are guided by the use of automatic target trackers, which are additionally manually corrected by an operator based on guidance laws, in which an essential portion of the guidance command is formed from the speed of rotation of the line of sight from the tracker to the target. The estimated value of the speed of rotation for the guidance is improved by the subject of the present invention.
The essential portion of the guidance command is formed in the guidance laws of the PN family from the speed of rotation of the line of sight between the missile (M) and the target. To do so, the speed of rotation of the target line of sight is provided by a homing head, which automatically tracks the target. Equation (1) describes this prior-art guidance law for guidance based on the transverse acceleration in the yawing plane:                               a          FYK                =                                                            V                A                            ·              Λ                                      cos              ⁡                              (                                                      ψ                    F                                    -                  ψ                                )                                              ·          ψ                                    (        1        )            
in which
aFYK=transverse acceleration command to the M in the yawing plane,
VA=velocity of approach between the M and the target,
xcex9=navigation constant,
-("psgr"Fxe2x88x92-"psgr") =swiveling angle of the homing head in relation to the longitudinal axis of the M, and
"psgr"=speed of rotation of the line of sight between the M and the target.
The most important variable for calculating the guidance command aFYK is the speed of rotation "psgr". Its quality substantially affects the hitting performance of the guided missile (GM). Variables containing errors in the term VAxc2x7A/cos ("psgr"Fxe2x88x92"psgr") have a substantially weaker effect on the hitting performance of the GM. Other terms of the guidance law, e.g., the compensation of the effect of the longitudinal acceleration of the M, are known and cause no change in the dominance of the speed of rotation of the line of sight with respect to the smallest possible error of hit of the GM.
An essential part of the guidance command, namely, the feed-forward term, is also formed from the speed of rotation and the angular acceleration of the line of sight to the target in the guidance laws of the LOSG (line-of-sight) guidance family. The speed of rotation of the line of sight is generated and made available for the guidance by a tracker, which in this case, automatically tracks the target as well. The angular acceleration can be formed in LOSG by a numerical differentiation and filtration from the speed of rotation provided.
The following considerations equally pertain to guidance systems with automatic target trackers in the guidance package or in the missile (homing heads). Trackers, which make possible a manual correction of the track point by an operator, are presupposed in both cases.
The primary object of the present invention is to guide the missile even during the track point corrections, possibly without overshooting and without delay. This means, e.g., that the collision course to the corrected track point is reached in the case of PN guidance rapidly and without overshooting, and that the GM is guided to the desired, corrected line of sight directly and without overshooting in the case of the line-of-sight guidance.
As a result, small hitting errors will be obtained even in the case of unsteady correction behavior of the operator and in the case of track point corrections shortly before the hit.
This object is accomplished according to the present invention by the following idea. The speed of rotation of the line of sight, which is formed by means of a target tracker in the known manner, is corrected by a variable that is derived from the correction signal of the operator for shifting the track point such that the components caused by apparent target maneuvers are compensated as a consequence of the correction. This corrected speed of rotation of the line of sight is used to form the guidance command in the known manner.
The estimated value of the rotation speed of the line of sight is formed for guidance in a freely programmable digital computer. The target tracker can include either an IR camera, a daylight camera, a radar sensor, a sound wave locating device or any similar tracking device. The target tracker, or one or more of its sensors, can be included in the projectile, or the target tracker can be located outside the projectile.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.